Universes
by nahpstablook
Summary: When Frisk participates in an experiment involving alternate universes, they accidentally get stuck in another world. To get back to their original world, Frisk must venture through three universes, one at a time, until they get back to their own world. The universes, in chronological order, are StoryShift (ut-storyshift, Tumblr), Underfell and Underswap (underswapped, Tumblr).
1. About this Fanfiction!

Hey guys! So, I am going to be writing a new Undertale fanfiction called, as you already know, Universes! You probably already read the synopsis above, so we'll skip that part of the explanation! Now, in this intro, we're gonna talk about the different AUs planned out, some of the things that Frisk brought along, and other things! So... let's begin! :)

 **AUs**

The AUs used here will probably be some of the more popular AUs that I see around Tumblr! Here's the list!

 **1) Underfell:** Basically edgy Undertale. Like, monsters are downright cruel here. That's why the humans sealed them down in the Underground. Get ready for an adventure with cruel goat ladies, evil skeletons, sadistic fish ladies, insane lizard scientists, creepy killer robots... and, uh, one nice flower. That's better.

 **2) Underswap:** What if one character... was like another character?! In this world, the monsters' roles have been mixed up! For example, Sans is now a hardworking and overenthusiastic little skeleton, while Papyrus... uh, slacks off. Get ready for a mixed up adventure, where a lot of weird things happen..

 **3) StoryShift (my favvv):** Similar to Underswap, but the characters are shifted rather than swapped. Get ready to meet a skeleton who watches over the Ruins, a determined goat warrior, an scientist goat man, an overdramatic fish TV star, and a king who's quite lazy. Oh yeah, and ASRIEL AND CHARA ARE ALIVE AND WELL.

 **Fanfiction Information!**

 **-** Frisk has contact with Undertale's universe. They still have their cellphone, which, strangely, works in other universes (totally not an excuse to include the UT characters' reactions to the other universes ehehe). This phone is freaking amazing, I mean, it can turn into jetpacks and store items. I want this phone now

\- No, Frisk will not meet the other Frisks from the universes they visit.

\- To get to the next universe, Frisk needs to pass the barrier of that AU in that universe's True Pacifist end. Storyshift and Underswap will have very similar Pacifist Endings compared to Undertale, BUT Underfell's Pacifist Ending is ENTIRELY DIFFERENT...

\- Frisk will not be able to speak. They use sign language, which everyone in every universe conveniently knows due to Gaster being there a long time ago.

Anyway, that's all the info about this story! Enjoy!


	2. Her Idea

" **CORRECT!"**

The human looked up at the television host, who appeared to be happy, despite his lack of facial features. They glanced over at Alphys, who was relieved. She wiped some sweat off her brow and gave a thumbs up, beaming. Oh, thank goodness the human didn't pick Undyne or Asgore. That would be... embarrassing, to say the least. She would freak out if Mettaton poked fun at her on live television.

"ALPHYS HAS A CRUSH ON... THE UNKNOWABLE." continued Mettaton. "YOU SEE, ALPHYS BELIEVES THAT THERE IS SOMEONE OUT THERE. SOMEONE WATCHING HER. SOMEONE WHO THINKS SHE IS 'CUTE' AND 'INTERESTING'." He turned to the camera and waved.

"HELLO, THEORETICAL PERSON. ALPHYS LIKES YOU."

He paused, and chuckled. "TOO BAD YOU ARE NOT REAL."

Alphys glared at the robot. "H-hey!" she exclaimed. "I.. I did research! There are alternate universes out there!"

"YOU SAID THE SAME THING ABOUT MEW MEW KISSY CUTIE," Mettaton shot back, mockery clear in his voice.

Alphys groaned, as her friend went back to the original script, wrapping up the 'deadly game show' the two of them had planned before the human had arrived. She thought about that. Alternate universes. She knew that they were out there. But.. how could she access them? How could she learn more about them? What if there was a way to visit an alternate universe? Questions filled her head, and she was even more curious about this topic than ever.

Finding a way to get to another universe was now her top priority!

..Well. Maybe not her top priority. That was an exaggeration. There was still the.. Amalgamates in the basement and her act with Mettaton that were more important. Speaking of her act with Mettaton.

She turned to the human, who was staring at her curiously. She noticed that Mettaton had already left the building (Did he fly through the roof? She wasn't paying attention.), and the child was waiting for something new to happen. Alphys opened her mouth to speak, but forgot what her line was. Damn it. She'd have to improvise.

"W-well, that was something.." Alphys managed to say.

* * *

 **Author's Notes - This was really short, sorry! I have a lot more planned for the next chapters, and I've already planned out how Frisk will react to the other worlds (Basically, they'll be disappointed and hurt seeing their friends cruel and sadistic in Underfell, and they'll be quite weirded out at Storyshift and Underswap.) Anyway, I hope you enjoy this fic!**

 **P.S: Yes, rectangular Mettaton speaks in all caps. Seriously, he speaks like that in the game.**


	3. The Experiment

It had been 6 months since the monsters arrived on the surface. Every monster had managed to settle down somewhere (turns out, gold was worth quite a lot on the surface, so it was easy to pay for housing), and the humans were surprisingly accepting of the newcomers. Monsters and humans lived on the surface together, in peace. It was just like how it was before the war happened. Everyone was happy.

Frisk and Toriel got a rather nice cottage together. It looked quite similar to Toriel's old home in the ruins, except it was made of wood. The front yard had pretty golden flowers on it, a small apple tree, and a white picket fence surrounding the entire house. There was a cute little welcome mat at the doorstep, embroidered with the message "Welcome Everyone!". Someone had scrawled below it "..except Asgore." Then, someone else had crossed the new message out. All of Frisk's closest friends lived quite close to their house, so Frisk could visit them easily. Occasionally, some of the monsters would go visit the two of them, just to greet them or hang out. It was great, honestly.

Frisk was coming home from school one day. The local school was just a ten minute walk from their neighborhood, so they walked home just about every day. They looked around. It was a rather beautiful day outside. Birds were singing, flowers were blooming... it was a fine day for a great game of catch. Frisk saw their house come into view, and smiled. They wondered what great things might happen today. Perhaps they could go hang out with Papyrus and Sans. Or maybe listen to music with Napstablook. Or maybe they could hang out at Alphys and Mettaton's place.

...Maybe they should just get home first.

The child opened the gate of the white picket fence and stepped through. Toriel was in the living room, reading yet another book about snails that she had recently borrowed from the local library. "Oh! Welcome home, Frisk!" she greeted happily. "There's some food in the kitchen, if you want. Papyrus and Undyne recently dropped off some spaghetti! Papyrus says that you love their spaghetti, correct?"

Frisk awkwardly nodded their head yes, even though Papyrus' spaghetti had an... uh, an _interesting_ flavor.

 _I think that I'll just eat some leftover pie from last night,_ Frisk signed. Toriel smiled, and nodded.

"Alright then, Frisk. Make sure to do your homework after eating." she said. Frisk nodded. _I will!_ they signed.

They took a plate from the cupboards and a slice of pie from the counter. They then proceeded to open one of the drawers, and took out a small fork. They sat down at the dining table and began eating their pie. Man. Toriel's pies were the best. If Frisk had to be honest, Toriel's cinnamon-butterscotch pie was the best food that they had eaten during their journey in the Underground.

 _Ring, ring._

Frisk looked over at their bag. Their cell phone was ringing. They quickly unzipped the bag and grabbed the cellphone to see who was calling.

It was Mettaton. His contact picture was simply a picture of him and Frisk taking a selfie together, after they had reached the surface.

They pressed the 'accept call' button.

"Hello, Frisk-darling! How's it been? Alphys told me to call you over to our place. She said that she wanted to show you something." He paused. "I actually have no idea what it might be. She's been working on some machine in her laboratory recently, and apparently, she doesn't want anyone coming in there. Except for Papyrus's brother, who comes around here occasionally. I heard her talking about... alternate universes or something?" The robot laughed. "Probably something about Mew Mew Kissy Cutie. Anyway, I'll see you around, beautiful!"

And then he hung up.

Frisk got up from the table and grabbed their bag. Mom, _I'm going to Alphys and Mettaton's place._ they signed quickly. Toriel looked up from her book, and smiled. "That's okay, Frisk. But make sure to be back by evening to get your homework done!" she called. Frisk nodded. _Okay! Bye!_

Alphys and Mettaton lived not too far away from Frisk's place. As we said earlier, all of Frisk's friends lived nearby their house. They arrived at the house. Or the mansion. Or something like that. What they mean was that Alphys and Mettaton's house was pretty damn big. Saying it was a mansion was an exaggeration, but saying it was a house was an understatement. You know what they meant. Alphys had a decently big room, with an even bigger laboratory downstairs. And Mettaton's room was huge. So, no wonder they had a big house. Let's stop talking about how big their house was, and move on.

They pressed the doorbell, and a rather loud sound could be heard. Sounded a bit like a jingle. Someone opened the door.

"oh, hey frisk." It was Sans. Frisk wasn't really surprised by this, since Mettaton had mentioned something about Sans coming over often during the phone call.

 _Hey, Sans! Alphys was looking for me, apparently._ Frisk signed. Sans nodded. "yep, she was. she's in her laboratory. go down the hall and down the stairs. the lab's in the basement." Frisk nodded their head in thanks. _Thanks!_

Frisk followed Sans' directions, and made it down to Alphys' laboratory. She was working on some machine. "O-oh! Hey Frisk! I didn't expect you so soon!" She put down her tools, and smiled. "B-but that doesn't really matter now." She gestured to the machine.

"Check it out."

The machine was about the same height as a fridge. Buttons and wires covered the sides, and on the front was a glass door. Above the glass door was a screen, with dials and more buttons next to it. The screen displayed three sets of letters - SS, UF and US. Frisk looked up at it all.

 _What is it?_ they asked.

Alphys smiled. "It's like a gateway to another universe." Frisk grinned. _Cool!_

"N-now Frisk. This may seem like a bit much, b-but.. could you test the machine out?" Alphys handed the child a small button. "It's... it's not dangerous. If you're ever in trouble, j-just press the button, and you'll be sent back to the machine, safe and sound!" Frisk took the button, and looked up at the scientist. _How long will this take?_ they asked.

"Just a few minutes, Frisk."

 _Okay, I guess. As long as it's safe._

Alphys beamed. "Great! Just get in the capsule, strap yourself in, and I'll pull the lever! Tell me how it goes, okay?" Frisk nodded, and followed Alphys' instructions. "A-are you ready? I'm about to pull the lever."

Frisk gave Alphys a thumbs up. This machine was safe... right?

Suddenly, they heard a loud buzzing sound, and all they could see was white. They couldn't feel themself strapped in anymore. They couldn't feel anything, for that matter. All they could feel was strong, rushing winds, blowing past their face. That, and their cellphone and the button that Alphys had given them. The winds became stronger. Frisk tightened their grip on the button, but all of a sudden...

It flew out of their hands.

Frisk struggled to grab the button. But when the button was just at their fingertips, the buzzing noise stopped, and everything went black.

* * *

 **Author's Notes: Okay, just for the sake of it, I'm gonna tell you all about the housing on the surface.**

 **-Frisk and Toriel live together, as described in the story. Frisk and Tori's place is basically the safe place where anyone can kind of come in if there's a problem at home, or if they just want to relax and eat pie. The door's usually open all day to everyone, and since they live in such a nice, friendly neighborhood, there are no burglars. At nighttime, however, the door obviously stays shut.**

 **-Sans and Papyrus live together. Their house looks exactly the same as the house in Snowdin. Everything about this house is basically the same, including the mailboxes and Papyrus' shed. Sometimes, Sans and Papyrus host little get-togethers at their place, and it's basically a place where anyone whom they know can hang out, eat food and watch television.**

 **-Undyne lives alone, but she's neighbors with Alphys and Mettaton. Most of the time, she stays at Alphys and Metta's place, just for a chance to hang out/date Alphys. Of course, she finds Mettaton EXTREMELY annoying, but she learned to live with it. Her house looks the same as her original house, which was burned down in the game. She even managed to recreate the giant anime sword that was burned along with the house.**

 **-Alphys and Mettaton live together, and their house is the biggest out of everyone's (since Metta's a famous tv star, and Alphys is a talented scientist, they managed to afford such a nice house). It has a huge laboratory downstairs. The lab will be the area where the UNDERTALE characters will spend most of their time in, since they're giving Frisk advice and tracking their progress. Undyne can also be considered to live here, since she comes over daily, sleeps over often, and has her own room.**

 **-Napstablook lives alone. Their house is basically a small, blue cottage with the same interior as Napstablook's old house in Undertale. Beside Napstablook's house, there are two cottages, one pink and one orange, in hopes that their cousins may return one day. Usually, when Undyne and Alphys are hanging out and dating in their house, Mettaton stays at the pink cottage. And occasionally, when Mad Dummy feels really stressed or whatever, he goes to the orange cottage. Napstablook STILL has not figured out Mettaton and the Mad Dummy's true identities. Somebody. PLEASE. TELL THEM.**

* * *

 **Also, the order of the Universes is going to be Storyshift to Underfell to Underswap. Because I honestly don't feel like writing Underfell right now, and I LOVE StoryShift. Anyway! Next chapter, we're starting StoryShift! The symbols [SS], [UF] and [US] indicate which universe the chapter takes place in. Now. This is where the story truly begins. I hope you enjoy it!**


	4. (SS) Once Upon A Shift

**_Long ago, two races ruled over the Earth. Humans and monsters._**

 ** _One day, war broke out between the two races. After a long battle, the humans were victorious. They sealed the monsters underground with a magic spell._**

 ** _Many years later._**

 ** _Mt. Ebott. 201X._**

 ** _Legends say that those who climb the mountain never return._**

A robot stumbles up the mountain. This robot has black, short hair, part of it covering his right eye. When he first got his body, he was told to keep his hair that way, since his face wasn't exactly finished yet. Actually, the exposed circuitry on his face would never be patched up. He would never be finished, anyway.

He is wearing a faded pink top, with a single black stripe around the middle. Black pants, and faded pink boots, matching the shirt perfectly. An upside-down heart locket, colored yellow, hung from his neck. He regarded these clothes as 'simple', and he didn't really mind getting them that dirty. Besides, he has a whole wardrobe of fashionable clothing back home. He wouldn't mind getting a plain t-shirt and pants messed up.

But he decides not to think of home, for now.

Suddenly, rain begins to pour down from the sky. He groans. Rain. How fantastic.

His robotic body was not exactly built to be waterproof. And if he stayed any longer in this storm, he'd break down. And of course, nobody would go looking for him. Nobody would try to go fix him up, or retrieve him from the mountain if this ever happened. He'd be gone. Dead.

To avoid such terrible things, he would need to find shelter. Now panicked, the robot looks around. Any caves? Tents? Trees he could hide underneath?

Then, he spots it. In the distance, there was a small cave opening. It was partially covered in vines. He smiles, and runs towards the shelter before anything terrible could happen.

He manages to get inside the cave safely. He lets out a sigh of relief, knowing that he'd be okay. For now.

The cave is rather small. More vines could be seen hanging from the walls. There are also several insects crawling around.

But the most noticeable thing is the giant hole in the middle of it all.

The robot walks over to the hole and peers down. He can't even see the bottom. However, he could hear faint voices coming from the hole. Creepy.

This is just a horror movie waiting to happen, isn't it?

Curiosity gets the best of him, and he tries to get closer to the hole.

Suddenly, he trips on a vine and falls down the hole. DAMN IT!

He keeps falling, and falling. He knows that this is the end of his life. He starts to wish that he could have stayed in the rain. That might have been a better death than plunging face first into a seemingly bottomless pit.

Then, he lands in a bed of soft golden flowers.

He is alive.

The robot looks around. He is in an empty room. Well, almost empty, at least. The only thing in the room was this flower bed.

He looks around some more. Then, he notices a narrow hallway to his left. Great! Maybe he can find someone to help him.

He tries to get up, but he falls down again. The fall might not have broken him, but it definitely injured him.

The robot calls for help.

...

And somebody came.

"oh... there you are... i thought i heard someone over here..."

* * *

 **A/N: I LISTENED TO MEGALOGLAMOUR ON LOOP WHILE WRITING THIS AND IT'S ACTUALLY REALLY GOOD GOOGLE IT IF YOU HAVEN'T HEARD IT**

 **Also, this is the beginning of the story! I hope you enjoy the first part of this story, StoryShift!**


	5. (SS) Something Quite Different

**Author's Notes: Okay, so the past few chapters MAY have been weird. Forgive me. But I guess we're starting the actual story here? So.. here we go.**

* * *

Frisk awoke on a familiar bed of golden flowers. Hm. Did the machine work? Or did they get sent back to the start of their journey? They looked around. Everything looked.. basically the same. This room gave them nostalgia, actually. This was where their journey began, wasn't it? Well.. at least it _looked_ like the place where their journey started..

Suddenly, their phone began ringing. They took it out of their pockets. It was Alphys, requesting a video chat. Frisk tapped the accept button.

"Hey, Frisk, are you.. alright? What happened?"

I dropped the button..

"W-what? Oh god, no. Oh, no, no, no, NO!"

Alphys set the phone down on a table and started pacing around.

"That means you lost connection with the machine! T-that means.." Alphys gulped, as if she didn't want to tell Frisk something.

What? What is it? Frisk signed quickly.

Alphys sighed. "It means that you must cross the three nearest universes to get back to ours.. and that must be a real struggle for you..!"

Um, okay. How do I get to the next universe? Frisk asked.

"Well.. here's the hard part. You have to cross the barrier in every universe to get to the next one. B-but don't worry! I'm sure you can do it!" Alphys said.

Frisk smiled, and nodded. Alright then.

"I have to go. But I'll tell everyone what happened.. maybe they can give you some tips along the way. God, I'm so sorry.. I've messed up again, haven't I? W-what will Toriel say..?"

 _It's alright,_ Frisk signed. _I'm pretty sure I can make my way through these worlds.._

"Ehehe.. okay then, Frisk. Call us whenever you need help.. okay?" Frisk smiled at their friend and gave a thumbs up. Alphys smiled back.

"A-alright then! See you around!" Alphys proceeded to hang up.

* * *

Okay. Time to start a new adventure. Frisk felt a bit scared. What could be in these new universes? What if there was something dangerous there? What if they couldn't get back to their own world? What if there was something terrible and gruesome here?

..There was only one way to find out.

Frisk got up from the flower bed and dusted off their shirt. Onwards. To a new adventure.

Frisk cautiously walked down the narrow hallway to the left of the flower bed. They knew what would be coming next.. right? They made the turn, and there he was.

Flowey the Flower.

"Howdy! I'm FLOWEY! FLOWEY the FLOWER!" greeted the small plant. Great, we're going through this again. Frisk wouldn't fall for As- FLOWEY'S tricks this time. They knew they had to dodge the pellets, as opposed to running into them as Flowey advised they do. They weren't stupid.

After Flowey's familiar spiel, he launched a barrage of bullets towards the small child. Frisk dodged them swiftly. Flowey looked up at Frisk. "Hey... buddy. You missed them. And that makes me... sad. Let's try this again." The bullets came again, and Frisk stepped to the side, avoiding the attacks with ease. Flowey glared at the brown haired kid. "..What's wrong with you? Do you have... some kind of problem? This is the last time, friend." The bullets, yet again, flew at Frisk. Frisk proceeded to dodge the bullets easily. And then, the flower's face changed into a more demonic and terrifying one. Been there, done that. Was this universe just the exact same?

"You know what's going on here, don't ya? You just wanted to see me suffer."

The bullets surrounded Frisk and their soul, and they slowly closed in.

"Now, DIE."

Frisk, unlike their first encounter with Flowey, did not freak out and scream for help like their lives depended on it. Pfft. They knew that Toriel would come and kick Flowey's butt in 3.. 2... 1...

The bullets disappeared, and Frisk was restored to full health. Flowey, shocked, turns to the side to see who the hell saved this kid from death. "What?!" he asked angrily.

Suddenly - and unexpectedly - a large, white bone came flying at Flowey. Flowey screeched, and got knocked to the side. Frisk's heart skipped a beat. Alright, this was not normal. What gives?

Frisk looked up to see a familiar face.

"AH! A HUMAN! THAT STRANGE FLOWER WAS TRYING TO HARM YOU! BUT DO NOT FEAR!"

He placed his hand on his chest and looked up heroically.

"I, THE GREAT PAPYRUS, GUARDIAN OF THE RUINS, HAS SAVED YOU! NYEH HEH HEH!"

 **A/N: Oh my god, I'm so sorry that I haven't updated in months! I've been doing other things, like catching up on schoolwork, going on trips, reading webcomics... yeah. Sorry 'bout that!**


End file.
